st165,st 185, st105 trans questions

my car is the 165. I know depending on year and model the gear ratio changed. So if I change the transmission does that mean I have to swap out my rear gear ratio as well to match or is all the changes done before hitting the center diff?

Guess what I'm saying did the transmission gears just change or did the final gears change as well?

The final gear ratio is the same for all the different trans options. You can swap in any of them without worrying about the diff ratios.